<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <script src="../lib/react.development.js"></script>
    <script src="../lib/react-dom.development.js"></script>
    <script src="../lib/babel.js"></script>
</head>
<body>
<div id="example"></div>
<script type="text/jsx">

    class Clock extends React.Component {
        constructor(props) {
            super(props);
            this.state = {date: new Date()};
        }
        componentDidMount() {
            this.timerID = setInterval(
                    () => this.tick(),
                    1000
            );
        }
        componentWillUnmount() {
            clearInterval(this.timerID);
        }

        tick() {
            this.setState({
                date: new Date()
            });
        }
        render() {
            return (
                    <div>
                        <h1>Hello, world!</h1>
                        <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
                    </div>
            );
        }
    }
    ReactDOM.render(
            <Clock />,
            document.getElementById('example')
    );

</script>
</body>
</html>